Cryogenic tank

Abstract

Cryogenic tank having a structure for holding an inner shell ( 2 ) in an outer shell ( 3 ), with a first connection ( 5 ) between the first end ( 21 ) of the inner shell ( 2 ) and the first end ( 31 ) of the outer shell ( 3 ), and a second connection ( 6 ) between the second end ( 22 ) of the inner shell ( 2 ) and the second end ( 32 ) of the outer shell ( 3 ), the first connection ( 5 ) being integrally secured on the one hand to a curved region of the dome ( 31 ) of the first end of the outer shell ( 3 ) and on the other hand to a curved region of the dome ( 21 ) of the first end of the inner shell ( 2 ), the second connection ( 6 ) being integrally secured on the one hand to a curved region of the dome ( 32 ) of the second end of the outer shell ( 3 ) and on the other hand to a curved region of the dome ( 22 ) of the second end of the inner shell ( 2 ).

What is claimed is: 
     
         1 . A cryogenic tank for storing liquefied fluid, comprising an inner shell delimiting a storage volume for liquefied fluid and an outer shell arranged around and spaced apart from the inner shell, the space between said inner and outer shells comprising a thermal insulation, the inner and outer shells extending in a longitudinal direction between two longitudinal ends, the inner and outer shells having, at each longitudinal end, a dome-shaped portion, the tank comprising a structure for holding the inner shell in the outer shell, the holding structure comprising a first mechanical connection between the first longitudinal end of the inner shell and the first longitudinal end of the outer shell, and a second mechanical connection between the second longitudinal end of the inner shell and the second longitudinal end of the outer shell, the first mechanical connection being integrally secured on the one hand to a curved region of the dome of the first end of the outer shell and on the other hand to a curved region of the dome of the first end of the inner shell, the second mechanical connection being integrally secured on the one hand to a curved region of the dome of the second end of the outer shell and on the other hand to a curved region of the dome of the second end of the inner shell, each dome-shaped portion having a cross section, in a plane orthogonal to the longitudinal direction, having a width that ranges between a minimum width, at the longitudinal end, and a maximum width, the first mechanical connection being integrally secured to the dome of the first end of the outer shell in a region where the width of the section of the dome of the outer shell is between 50% and 100% of the maximum width, wherein the first mechanical connection is integrally secured to the dome of the first end of the inner shell in a region where the width of the section of the dome of the inner shell is between 50% and 100% of the maximum width, and in that the first and/or the second mechanical connection comprises several bearing structures distributed angularly around a central axis, and in that the bearing structures form part of a connection ring extending around the central axis and delimiting an open volume the section of which, in a plane orthogonal to the central axis, has a monotonic variation when moving along the central axis. 
     
     
         2 . The cryogenic tank according to  claim 1 , wherein the second mechanical connection is integrally secured to the second end of the outer shell in a region where the width of the section of the dome of the outer shell is between 50% and 100% of the maximum width, and/or to the second end of the inner shell in a region where the width of the section of the dome of the inner shell is between 50% and 100% of the maximum width. 
     
     
         3 . The cryogenic tank according to  claim 2 , wherein at least one of the mechanical connections is integrally secured to the respective dome of the outer shell in a region where the width of the section of the dome of the outer shell is greater than 50% and strictly less than 100% of the maximum width, and/or integrally secured to the respective dome of the inner shell in a region where the width of the section of the dome of the inner shell is greater than 50% and strictly less than 100% of the maximum width. 
     
     
         4 . The cryogenic tank according to  claim 1 , wherein the first mechanical connection is rigidly attached to the outer shell and attached to the inner shell in such a way to allow movement and/or deform in response to a relative expansion and/or contraction of the inner shell. 
     
     
         5 . The cryogenic tank according to  claim 1 , wherein the connection ring has an inner face facing the dome of the inner shell and an outer face facing the dome of the outer shell, the inner face having a profile complementary to the profile of the dome of the inner shell, and/or the outer face of the connection ring has a profile complementary to the profile of the dome of the outer shell. 
     
     
         6 . The cryogenic tank according to  claim 5 , wherein the first and/or the second mechanical connection comprises at least three bearing structures, each comprising at least one internal protrusion protruding from the inner face of the connection ring and at least one external protrusion protruding from the outer face of the connection ring, the connection ring being integrally secured to the inner and respectively outer shell only at these protrusions. 
     
     
         7 . The cryogenic tank according to  claim 1 , wherein the bearing structures are uniformly distributed angularly around the central axis. 
     
     
         8 . The cryogenic tank according to  claim 1 , wherein the ring delimits an open volume the section of which, in a plane orthogonal to the central axis, has a monotonic variation when moving along the central axis, the open volume having a section of substantially elliptical or circular shape. 
     
     
         9 . The cryogenic tank according to  claim 2 , wherein the holding structure comprises only the first and second mechanical connections. 
     
     
         10 . The cryogenic tank according to  claim 1 , wherein the holding structure comprises at least one third mechanical connection positioned longitudinally, along the longitudinal axis, between the first mechanical connection and the second mechanical connection. 
     
     
         11 . A method for assembling a tank according to  claim 1 , the longitudinal axis being horizontal during assembly, comprising the following successive steps
 a) attaching the first mechanical connection to the dome of the first end of the inner shell;   b) inserting the assembly thus obtained into the outer shell;   C) attaching the first mechanical connection to the dome of the first end of the outer shell.   
     
     
         12 . The method for assembling a tank according to  claim 1 , the longitudinal axis being vertical during assembly, comprising the following successive steps
 a) attaching the first mechanical connection to the dome of the first end of the outer shell;   b) inserting the inner shell into the outer shell;   c) attaching the first mechanical connection to the dome of the first end of the inner shell.